It is conceivable that greater use is being made of new battery systems (rechargeable battery systems), for example having lithium ion rechargeable batteries, lithium polymer rechargeable batteries or nickel metal hybrid rechargeable batteries, both in the case of stationary applications, for example wind turbines, and also in the case of mobile applications, for example in the case of electric vehicles (EV) or hybrid electrical vehicles (HEV) as rechargeable electrical energy storage devices (EES).
A battery system comprises a multiplicity of battery cells by way of example cylindrical or prismatic battery cells. As a result of their internal cell resistance and the electrochemical processes that are taking place, the battery cells become warm during the charging and discharging procedures. The battery cells can be connected in series in order to increase the electrical voltage and/or said battery cells can be connected in parallel in order to increase the maximum electrical current. The battery cells can be combined to form battery modules or battery units. When using said battery cells to drive vehicles, it is possible by way of example to connect approx. 100 battery cells (as a traction battery) in series or in parallel with one another.
A lithium ion battery cell comprises a positive electrode (cathode) and a negative electrode (anode) that can store in a reversible manner (intercalation) lithium ions (Li+) during the charging procedure or can discharge (deintercalation) lithium ions (Li+) during the discharging procedure. As a consequence, a periodic volume change of the electrodes occurs during the charging/discharging procedure and said change can be in the range of approx. 10% to approx. 30%. The volume change of the electrodes causes mechanical work in the electrodes and battery cells and this accelerates the aging process of the battery cells and thus shortens the serviceable life of the battery cells. Moreover, the electrodes “swell up” over the serviceable life of the battery cells, as a result of which the volume of the electrodes and the battery cells continues to increase in size over the serviceable life. Whereas cylindrical battery cells (round cells) are more or less stable owing to their winding geometry. prismatic battery cells and pouch cells should be stabilized from the outside by means of a force that counteracts the increase in volume. The force can be produced by way of example by means of clamping the battery cells in a pack frame of a battery module.
FIG. 1 illustrates a schematic view of a battery module 10 in accordance with the prior art.
The battery module 10 comprises a multiplicity of prismatic battery cells 1001 . . . 1004, which are arranged adjacent to one another, and a pack frame, which comprises a first end plate 2101, a second end plate 2102, a first clamping band 2201 and a second clamping band 2202 and encompasses and clamps the multiplicity of prismatic battery cells 1001 . . . 1004. The production process of the battery module 10 can include by way of example arranging the multiplicity of battery cells 1001 . . . 1004 between the first end plate 2101 and the second end plate 2102, applying an external force to the end plates 2101, 2102, so as to join the multiplicity of battery cells 1001 . . . 1004 and fasten the clamping bands 2201, 2202 to the end plates 2101, 2102, by way of example by means of a multiplicity of weld connections 21511 . . . 21522 so as to receive the force 9201, 9202, that counteracts the force of the multiplicity of joined battery cells 1001 . . . 1004.
The document DE 10 2014 204 245 that had not yet been published on the date of application of the present invention discloses an energy storage unit having a multiplicity of galvanic cells, wherein the cells in each case comprise outer contacts that are integrated in a cell housing (nutshell-cells) and the end plates comprise integrated contact plates or conductor plates.
In order to further increase the functionality and serviceable life of batteries (rechargeable batteries) and battery systems (rechargeable battery systems) and to further simplify their production process, it is however necessary to provide an improved clamping device for the battery cells.